1. Field of the Invention
The present invention relates to a loading and unloading station for semiconductor processing installations with a closeable charging opening through which wafer-shaped or disk-shaped objects which are accommodated in a transporting container can be loaded, unloaded and reloaded after removing a closure or through which a transporting container can be loaded or unloaded.
2. Description of the Prior Art
For the purpose of charging semiconductor processing installations, it is known to use so-called SMIF (Standard Mechanical Interface) boxes as magazine containers with a relatively small enclosed volume in which wafer magazines can be stored and transported. The box can be placed on an opening mechanism in an enclosure or housing which encloses one or more work stations so as to keep them free of dust. The box and opening mechanism have closing elements which are adapted to one another and which can be opened simultaneously one above the other so that dust particles resting on the outside of the closing elements can be enclosed therebetween when the wafer magazines are lowered into the housing together with the two closing elements. The box itself encloses the opening formed in the housing.
The SMIF(Standard Mechanical Interface) system was devised,, to reduce particle contamination by significantly reducing particle fluxes onto wafers. This end is accomplished by mechanically ensuring that during transport, storage and processing of the wafers, the gaseous media (such as air or nitrogen) surrounding the wafers is essentially stationary relative to the wafers and by ensuring that particles from the ambient outside environment do not enter the immediate internal wafer environment.
A loading and unloading device according to the German Patent 43 26 309 C1, for example, or a device having another operating sequence serves to remove the magazines from the transporting containers and place them in the processing installation. After the semiconductor wafers are processed, the magazines are transported back in the transporting containers.
The technique of SMIF boxes is especially suited for semiconductor wafers with smaller diameters, as is conventional. In view of the material characteristics of the semiconductor wafers, these SMIF boxes and the wafer magazines used with them are becoming increasingly unsuitable as transporting containers as the diameter of semiconductor wafers increases.
Transporting containers which take over the function of magazines at the same time are already known for semiconductor wafers of this type. Loading, unloading and reloading of the semiconductor wafers is effected individually in a plane parallel to the surface of the semiconductor wafers, wherein the transporting container can be closed by a container cover extending substantially at right angles to the loading and unloading plane. Accordingly, in contrast to the SMIF box, the container cover is removed and inserted laterally rather than in a downward direction.
Since the transporting containers are enclosed by a space with low requirements, as regards cleanness and since there are no magazines which can be loaded and unloaded such as those used in the SMIF technique, the charging of semiconductor processing installations proceeding from these transporting containers and the transporting back from such installations into the transporting containers presents problems. Moreover, the problem is exacerbated in that optional loading and unloading into and out of a greater number of transporting containers must be ensured under certain circumstances and the containers themselves must be supplied and removed by operating personnel under favorably ergonomic conditions.
An arrangement for storing, transporting and inserting substrates is known from EP 542 793 B 1. In this arrangement, a cassette with a lateral closing cap is arranged opposite a loading slot. The cassettes are brought into the loading position one after the other by a lifting plate which can hold a packet of stacked cassettes. When this position is reached, the closing cap is swiveled open at one edge and the substrate wafer is inserted into the clean room by a drawer which can travel out of the cassette. An air flow exiting from the loading slot prevents particles from penetrating into the clean room in that it passes through an open gap between a protruding seal and the cassette.
A significant improvement over the foregoing concepts has been presented in U.S. Pat. No. 5,772,386 to Mages et al., the entire disclosure of which is incorporated herein by reference.
Previous systems for semiconductor cassette and pod automated material handling systems (AMES) utilized over head transport technology (OHT) or guided vehicle technology. AMHS systems shuttle material to and from processing or inspection tools within the semiconductor fabricating facility.
OHT systems typically transport material with carts that proceed on tracks or rails mounted above tool charging openings or loading ports. Material is transferred from a cart and lowered onto and raised from the load ports utilizing a hoist mounted on the carts.
Guided vehicle systems typically transport material with vehicles that operate on the floor of the semiconductor fabricating facility. The guided vehicles proceed on rails mounted to the floor, follow slots formed in the floor, or are self guided typically by RF signals from wires embedded in the floor or via optical tape attached to the floor, or by dead reckoning, or by use of other suitable references. Material is transferred from the guided vehicle and lowered onto and raised from the loading ports utilizing a multi axis robot mounted on the guided vehicle.
It was with knowledge of the foregoing state of the technology that the present invention has been conceived and is now reduced to practice.
The present invention relates to a system for loading and unloading semiconductor wafers. The system of the invention, which may be used adjacent a process tool having a reception region, includes a frame having a charging opening which may be in communication with the reception region of the process tool, a platform mounted on the frame and movable between a deployed position and a retracted position, and a movable closure for the charging opening for opening and closing a horizontal path through the charging opening. In the deployed position, the platform has a generally level, or horizontal, orientation adjacent the charging opening and projects away from the frame for receiving thereon a cassette adapted to support therein a plurality of the semiconductor wafers to be passed though the charging opening. In one embodiment, the platform is elevationally movable on the frame between a retracted lowered position distant from the charging opening and a deployed raised position adjacent the charging opening. In another embodiment, the platform is rotationally movable on the frame between the deployed position having a generally level orientation located generally adjacent the charging opening and the retracted position folded against the frame. The loading and unloading system includes a transport system for advancing a cassette from a remote location and delivering the cassette to the platform. The transport system includes a nest member for supporting a cassette at spaced apart locations enabling reception therebetween of the platform so that the cassette can selectively be transferred, in one instance, from the nest member to the platform and, in another instance, from the platform to the nest member.
As compared to known guided vehicle systems, the present invention eliminates the need for a multi-axis robot mounted on the guided vehicle and also reduces or eliminates the floor space needed at the tool in the fabrication facility for operation of the guided vehicle. The invention recognizes that floor space of a fabrication facility is very expensive. As compared to OHT systems, the present invention eliminates the need for a hoist. The AMHS system of the present invention utilizes guided vehicles which can operate on the floor space completely or at least partially below the tool loading ports or charging openings.
In a first embodiment, the frame encompassing the loading port is equipped with a tilt drive that allows the tool loading port""s FOUP Front Opening Unified Pod) platform, or supporting surface, to be tilted from a level loading plane. As previously noted, for some time now, it has been known to employ transportable SMIF boxes, containers, or carriers, for maintaining articles, such as semiconductor wafers, clean. This has been achieved by maintaining within each carrier a substantially particle free environment while the wafers are being brought to, or removed from, the process tool. Previously, it was customary to carry a large number of the wafers within the carrier by supporting them in a spaced relationship by means of a cassette. Using this technique, the cassette would be loaded with a supply of wafers, transported into the carrier, then subsequently wafers would be removed from the cassette within the carrier one by one for placement in a load lock or the cassette would be transferred with the wafers within the clean mini-environment existing between the carrier, SMIF box, or the like, and the wafer processing equipment. The SMIF box was a bottom loading design and generally was used to carry substrates sized to a diameter of 200 mm. More recently, carriers are of the FOUP design intended to carry substrates sized to a diameter of 300 mm.
Returning now to a discussion of the AMHS system of the present invention, the guided vehicle is equipped with a lift fitted with a nest member for supporting the FOUP when the FOUP is being transported about the fabrication facility. To load a FOUP from the guided vehicle to the loading port, the following steps are performed.
(a) the platform, or FOUP supporting surface, but without a FOUP, is tilted to a retracted position;
(b) the guided vehicle with a nest supporting the FOUP during transit is positioned at the loading port;
(c) the nest now supporting the FOUP is raised to a level of a loading plane at the charging opening;
(d) the platform, or FOUP supporting surface, is tilted to the horizontal loading plane; and
(e) with the nest and the platform proximately and interdigitally positioned, the nest is lowered thereby transferring the FOUP to be supported on the platform and the nest without the FOUP thereon continues to be lowered. Steps (a) and (b) can be performed simultaneously. Unloading the FOUP from the platform and transferring it to the nest requires an opposite sequence of steps.
In a second embodiment, the frame encompassing the loading port is equipped with a lift drive that allows the tool loading port""s FOUP platform, or supporting surface, to be lowered from the horizontal loading plane. The guided vehicle is equipped with a nest member including a pair of spaced forks for supporting the FOUP when the FOUP is being transported about the fabrication facility. When the lift drive is in the lowered position, the loading port""s FOUP supporting surface, or platform, is located elevationally below the forks. To load a FOUP from the guided vehicle to the loading port the following steps are performed:
(a) the platform, or anticipated FOUP supporting surface is lowered or already at the lowered position;
(b) the guided vehicle is located at the loading port;
(c) the nest with the FOUP supported thereon is raised; and
(d) the guided vehicle is removed from the loading port.
To unload a FOUP from the loading port and return it to the guided vehicle, the following steps are performed:
(a) the guided vehicle is positioned at the loading port;
(b) the nest with the FOUP thereon is lowered;
(c) the guided vehicle is removed from the loading port;
(d) the lift is raised or left at a lowered position.
A primary feature, then, of the present invention is the provision of a loading and unloading system for semiconductor processing installations with a closeable charging opening through which wafer-shaped or disk-shaped objects which are accommodated in a transporting container can be loaded, unloaded and reloaded after removing a closure or through which a transporting container can be loaded or unloaded.
Another feature of the present invention is the provision of such a system incorporating a platform mounted on a frame encompassing the charging opening, the platform being movable between a deployed position and a retracted position, the platform in the deployed position having a generally level orientation adjacent the charging opening and projecting away from the frame for receiving thereon a cassette adapted to support therein a plurality of the semiconductor wafers.
Still another feature of the present invention is the provision of such a system in which the platform includes a shuttle stage and a cassette mount having an upper surface for receiving the cassette thereon when the platform is in the generally level orientation reciprocally mounted on the shuttle stage with the cassette thereon in plane between a withdrawn position distant from the charging opening and an advanced position proximate the charging opening.
Yet another feature of the present invention is the provision of such a system in which the platform is rotationally movable on the frame between the deployed position having a generally level orientation located generally adjacent the charging opening and the retracted position folded against the frame.
Still a further feature of the present invention is the provision of such a system in which a transport system is employed for advancing a cassette containing a plurality of semiconductor wafers from a remote location and delivering the cassette onto the platform when in a generally level orientation.
Yet a further feature of the present invention is the provision of such a system wherein the transport system includes a nest member for supporting a cassette at spaced apart locations enabling reception therebetween of the platform in the deployed position so that the cassette can selectively be transferred, in one instance, from the nest member to the platform and, in another instance, from the platform to the nest member.
Other and further features, advantages, and benefits of the invention will become apparent in the following description taken in conjunction with the following drawings. It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory but are not to be restrictive of the invention. The accompanying drawings which are incorporated in and constitute a part of this invention, illustrate one of the embodiments of the invention, and together with the description, serve to explain the principles of the invention in general terms. Like numerals refer to like parts throughout the disclosure.